diesel fuel consumption reduction in a dairy industry by application of solar thermal technology

8/12/2019 Diesel fuel consumption reduction in a dairy industry by application of solar thermal technology

1/5

Abstract

This work analyses the fraction of total load that can besupplied by solar thermal technology using flat platecollectors. DDC, Lainchaur, which processes 60,000 litre ofmilk per day has been taken as the basis for this study, sincemost of the private dairy industries are smaller than this.

Technically, two isolated solar thermal storage tanks wereused in conjunction with a collector array. The hot watercollected from the first tank at the end of each day would beused in the boiler as feed water in the next morning. Thesecond tank would then be used to store hot water for the nextday. In this way each tank would supply and store energy onalternate days.

Initial screening was done by simulation using Matlab fromwhich the average temperatures that can be achieved per dayfor each month in a water storage tank of 2,500 litres werecalculated and total energy gained annually on thistemperature basis was calculated. Again, the total energy

gained annually was calculated by total area of collector used.Energy gained by the area basis was found to be more by7.17% only. This was due to the fact that losses in tank andconnecting pipes were not accounted while calculating by areabasis. The legitimacy of the above findings were checked byF-Chart [6] method and found that the fraction of total loadsupplied by area basis was only 1.17% more than thatcalculated value from F-chart method .Thus all furthercalculations were carried out using area basis.

It was determined that use of Solar Water Heating Systemwith 55 square meter of collector area and two insulated hotwater tank storage of 2,500 litres capacity each, can reduce thediesel fuel consumption by 5,843.27 litres annually for the

size of the dairy considered i.e. a dairy of capacity of 60,000litres milk processing per day. The CO2 emission reducedby15, 659.98 kg annually. The project is financial viable sinceits Net Present Value is positive.

Index terms: Solar radiation, Solar thermal system, Total fraction,

F-chart.

1. Introduction

Most industries in Nepal use diesel and kerosene boilers tomeet their hot water requirements. Some of the industries thatheavily depend on fossil fuel boilers for hot water are: hotels,dyeing factories, carpet washing factories, breweries, and

dairies. Efficient solar water heaters can replace water boilersin hotels, dyeing and carpet washing industries almostcompletely and can be used to preheat water up to 60 degreecentigrade in breweries and dairies. With these industriesusing diesel and kerosene for heating water, large amounts ofGHGs are emitted every day. Under the recent energy scenariowhere fossil fuel prices are skyrocketing, using high efficiency

solar water heaters can be a potential alternative. Meanwhile,the solar water heating technologies are getting more efficientand affordable. The upfront investments required installing alocally assembled high quality solar water-heating system canbe paid back within 3 to 4 years from the savings madethrough avoided use of fossil fuels. Solar water heatingsystems are available with 20 plus years of "trouble free"guarantees. This proves solar water heating systems to bemuch more economical than diesel/kerosene boilers in termsof life-cycle cost. Apart from being economical, solar waterheaters are environment friendly. They are zero-emissionenergy providers and contribute towards cleaning the local airas well as reducing GHG emissions.

2. Research methodology

Every research needs systematic tools and methods in order tomake remarkable achievements. Nowadays simulation of themodel in computer is done at first in order to assess thefeasibility of the actual model as well as to realize theperformance of the system in advance. Then only the realmodel is built and experiment is conducted in it. In thisresearch also, the basic steps followed during the studyperiods are:

a. Solar thermal System Design

b. Simulation of the Solar Thermal System

c. Financial Analysis

2.1. Design of Solar Thermal System

The solar thermal system design is done for the boiler used inthe DDC, Lainchaur, Kathamandu, which processes 60,000litres of milk per day. The designed solar thermal systemwould be used to heat the feed water of the boiler. The designis done under the consideration that certain amount of water isheated in a day by solar thermal system is stored in highlyinsulated tank which is used next day as feed water to theboiler. As rule of thumb 50 to 100 litres of water storage isrequired for per square meter of collector area [17]. From

Study on Diesel Fuel Consumption Reduction in DairyIndustries by Application of Solar Thermal Energy.

Ramendra Kumar Rabindra Nath Bhattarai

M.Sc. Renewable Energy EngineeringPulchowk Campus, Institute of Engineering

Tribhuvan University

Professor, Department of Mechanical Engineering,Pulchowk Campus, Institute of Engineering

Tribhuvan University


2/5

observation in DDC, Lainchaur, water consumed by boiler pershift per day is 1,820 litres and for design purpose 2,500 litresof water is taken. Here 55 m2of collector area would be used.Depending on different observations and readings that weretaken in the boiler under running condition in DDC, Lainchaur

the solar thermal system is designed.

2.2. Solar radiation IntensityThe solar radiation data taken from NASA and compared withdata of SWERA [12] and noted that annual average differencebetween the data from the two sources is only 1.159 %, thusthe data provided by NASA can be used with negligible error.Therefore the radiation data for tilted surface is directly usedfrom the data provided by NASA.

2.3. Inlet Water Temperature for Load AnalysisTable: 2.3 below show the monthly average temperature ofKathmandu [9] which is used as the inlet water temperature to

the solar thermal collector and used in load analysis.

2.4. Simulation of the Solar Thermal SystemThe performance of the systems as shown in figure 2.4 wasmodeled by a simulation program written in MATLABprogramming .The program calculates the solar gain for thespecified system based on the insolation ,ambient temperature,the latitude ,the parameters specifying the solar collectorsystem and the volume of storage tank. Since the daily hourlyradiation data is not available, average monthly insolation andsimilarly average monthly ambient temperature is used forcalculation .The simulation gives the maximum temperaturethat the storage tank water can attain at end of each day of

each month in average. Finally the average monthly dailytemperatures are used to calculate the maximum energy permonth and then annually that can be obtained by using thethermal system under consideration and load fraction suppliedby it.

Mathematical modeling of simple collector and storage tank:

During a particular instant energy balance equation of solarcollector relating the temperature Tco of the circulated waterat the solar collector exit and inlet temperature Tcin can begiven from equation:

(Tco-Tcin)**Cw= I*Area*

Where,

= Collector efficiency

Area = Area of collector

I = Irradiance

= mass flow rate

Cw= Specific heat of water

From which we can calculate temperature Tco of water exitform collector as given

Tco= Tcin+ (I*Area*)/(*Cw) .. (1)

The collector efficiency can be calculated using the equation:

= Fr()-(FrUc)*{(Ti-Ta)/I} (2)

Ti = Tcin=Inlet water temperature to the collector

Ta = Ambient temperature around the collector

From selected collector type and its efficiency () plot against

((Ti-Ta)/I), we can get

Fr() = Intercept of the plot

(FrUc) = Slope of the plot

Energy balance equation between collector and storage tankwith water:

For initial second:

m (Tco-Tcin) * Cw= M (TT-Tcin)

M = mass of water in storage tank

Solving we get: TT= Tcin+ (m *(Tco-Tcin))/M .... (3)

Now this temperature TTbecomes inlet temperature Tcin tothe collector for next second. In this way the temperature atthe end of last second of average each day per month iscalculated, where total number of second per average day isdetermined by multiplying peak sun hour of that day by 3,600s per hour.

TABLE: 2.3 AVERAGE TEMPERATURE PER MONTH (T, C)

Month Jan Feb March April May Jun July August Sept Oct Nov Dec

Temp. 8 11 16 20 22 23 23 23 22 18 14 10

Solar Collector

Tco

TT

Tcin

Storage

tank

P

M

Figure: 2.4


3/5

Output temperatures for 12 months individuals average perday (final temperature in table: 2.5a) are used for calculatingthe energy supplied by the installed system.

2.5.Calculation of Energy Delivered by Temperature Basis:In the table: 2.5a the average energy per month that can bestored at the end of each day in the storage tank has calculatedwhere initial temperature of the storage tank water is assumedto be equal to the average ambient temperature per day permonth.

A sample calculation for January:Average ambient temperature = CMass of water per shift per day = 2,500kgSpecific heat capacity of water = 4,200J/kgCFinal temperature that can be achieved at theend of the each day = 60.69CEnergy Per day in January = 2500*4200*(60.69-8)= 553.32MJAverage Monthly Energy Collected =

30*553.32=16,599.6MJ

Similarly calculating energy collected in remaining monthstotal energy delivered annually is obtained. Finally in thetable: 2.5b energy delivered by the thermal system annually isconverted into equivalent fuel saved and emission reduction iscalculated.

2.6.Calculation of Energy delivered by area basisNow in this section again maximum energy that can beprovided by the system considered has been calculated but onthe basis of area.

Table: 2.5b shows the equivalent fuel saved and emissionreduction on area basis.

2.7.Fractional Energy Supplied by Solar Thermal SystemIn this section the legitimacy of the data of diesel consumption

provided by DDC Lainchaur has been verified so that theexact fraction of total energy consumed by boiler that is beingprovided by the solar thermal system could be calculated.Theoretically the energy generated by the boiler in the form ofwater steam is calculated and using the efficiency of boiler0.6, the total amount of energy required to be given in boiler iscalculated which is converted in terms of total dieselconsumed. Now this calculated amount of diesel is comparedwith the data of diesel consumption annually provided byDDC, Lainchaur. Input energy to the boiler is calculated to be22,99010MJ annually. Equivalent Diesel required is63,159.61Litres annually. Comparing with the provided dieselconsumption data of the DDC, it is only less by 3.39 %

annually. This deviation is due to the fact that sometimes theindustry runs two shifts per day. After this analysis we canrely on data of diesel consumed annually provided by DDD,Lainchaur. Now fraction (F) of this energy being supplied bysolar thermal system can be calculated on area basis:

Total Fraction (f) =

Total energy supplied by Solar Thermal System

annually (in terms of diesel saving )

Total enrgy required by Boiler alone as input

annually(in terms diesel consumed )

= 5423.96/65377 = 0.0829 = 8.3%

TABLE: 2.5a ENERGY DELIVERED BY TEMPERATURE BASIS

MonthAv.Tem./ Month

(T C)

Vol. of WaterReq. /day shift (kg)

Cp(J/kg C)

Final Tem.(Th C)

Monthly Av./day Energy(MJ)

Avg. MonthlyEnergy(MJ)

Jan 8 2500 4200 60.6983 553.33215 16599.9645

Feb 11 2500 4200 68.4495 603.21975 18096.5925

Mar 16 2500 4200 75.7075 626.92875 18807.8625

Apr 20 2500 4200 78.2736 611.8728 18356.184

May 22 2500 4200 76.7833 575.22465 17256.7395

Jun 23 2500 4200 71.1249 505.31145 15159.3435

Jul 23 2500 4200 65.4118 445.3239 13359.717

Aug 23 2500 4200 66.9549 461.52645 13845.7935

Sep 22 2500 4200 66.6399 468.71895 14061.5685

Oct 18 2500 4200 72.9819 577.30995 17319.2985

Nov 14 2500 4200 70.0967 589.01535 17670.4605

Dec 10 2500 4200 63.6475 563.29875 16898.9625

Yearly En. (MJ)=197432.487


4/5

2.8.Fractional Energy Supplied by Solar Thermal Systemusing F-Chart method.

Sample calculation for January:

From specification of selected collector,

FR() = 0.706, FRUL= 4.19

Monthly average temperature, Ta = 8C

Standard reference Temperature, Tref = 100C

Monthly average solar radiation, HT =2 0.92 MJ/m2

Collector Area, Ac= 55m2

Monthly Average Load is taken from load analysis

Which is (using efficiency of boilers = 0.6)

L = 116942.55/0.6 = 19, 4904.25 MJ

X = FRUL *(Tref- T a) * *Ac/L

= 4.19*(100-8)*31*86400*55/ (116942.55*103)

= 0.47

Y = FR() n*H TN*Ac/L

= 0.706*20.92*106*31*55/ (116942.55*106)

= 0.21f = 1.029Y 0.065X 0.245Y2+ 0.0018X 2+ 0.0215Y 3

(For liquid system)

= 0.17

Similarly calculation for different months was done usingExcel spreadsheet. Finally, annually fraction of the loadsupplied by solar energy is calculated as:

F = fl/L = (12587.19)/(191584.17) = 0.0657 6.6 %

2.9.Financial Analysis:

The initial installation cost of the system would be NRs2,594,112.5.Since there was only one running cost ofcentrifugal pump and negligible repair and maintenance costfor initial 15 year, 3% of initial cost was taken as annualrunning cost. From area basis analysis, it was found thatannual amount of diesel fuel that could be saved is 5,423.96litres. Now using the price of diesel per litre NRs.100 [10],annual cost of fuel saved was calculated to NRs. 5, 36,972.04(5,423.96100).This saving in fuel cost was taken as theannual income.

Initial Investment (P) = NRs.25, 94,112.5

Annual Cost(C) =3% of P = NRs.77, 823.375Annual Income (E) = NRs. 5, 42,396

Useful Life of the System (N) = 15 Years

Discounted Payback period and Net Present Value werecalculated using four different interest rates 8%, 10%, 12%and 14% respectively. From calculation, it was seen that in allcases net present value is positive so the project is financiallyfeasible. Payback period increases from 8 to 12 years asinterest rates increases from 8% to 14%.

2.10. Results and ConclusionsThe solar water heating system with 55 square meters of

collector area and two insulated hot water storage tanks of2,500 litres capacity each was implemented in a dairy with acapacity of 60,000 litres milk processing per day. The resultsare listed below:

Fractional contribution by temperature basis and areabasis differs by 7.17% due to the fact that lossesin pipes and storage tank were not accounted whilecalculating by area basis.

Fractional contribution by area basis and F-chartmethod differed by only 1.7% which can beconcluded that the approach was in right direction.

TABLE: 2.5b FUEL AND EMISSION REDUCTION

Diesel Quantity Energy Equivalent

1 Litre 36.4MJ[5]

Temperature Basis

Annually Energy Saved by Solar Thermal System =19,7432.487 MJWhich is Equivalent =197432.487/36.4 = 5,423.96 Litre of Diesel

Saved Per year.

Area basisAnnually Energy Saved by Solar Thermal System =19,7432.487 MJ

Which is Equivalent =212695.3728/36.4 = 5,843.27 Litre of Diesel Saved Per year.

Diesel Quantity Burned CO2Emitted

1 Litre 2.68 kg[5]

Temperature BasisAnnually Diesel Saved=5423.96 Litre

Which is Equivalent =5,423.96*2.68=14,536.23 Kg of CO2 Emission reduced.

Area BasisAnnually Diesel Saved=5423.96 Litre

Which is Equivalent =5843.27*2.68=15,659.98 kg of CO2 Emission reduced.


5/5

It was found that 5,843.27 litres of diesel would besaved annually wherein present annual consumptionis 65,377 litres of diesel.

It was found that 15,659.98 kg of CO2 emissionwould be reduced annually.

In industrial sector an investment is taken asattractive if the payback period is 3 to 4 year. Thusthe system considered is not attractive frominvestors point of view as payback period is above 8year. Though being renewable energy system, it isstill beneficial from environmental point of view andNet Present Value is positive during the life span ofthe project.

Above findings led to the conclusion that solar thermaltechnology using flat plate and evacuated collector can beused to reduce the diesel fuel requirement for small to mediumscale dairy industry processing less than 60,000 litres of milkper day. That is economical and environment friendly. It is tobe noted that for large scale dairy industry and for largefractional contribution concentrated solar power should beused.

REFERENCES

[1] ASHRAE Standard, Methods of Testing to determine the thermalperformance of solar collectors. ANSI B198.1.197,1978

[2] Avda. Los Castros , Simulation of a solar domestic water heatingsystem with different collector efficiency and different storagetanks,Department of Electrical

[3] Engineering, E.T.S.I.I. yT., Cantabria University , Santander(Spain)Central Solar Hot Water Systems Design Guide, US ArmyCorpsl. of Engineers,Dec,2011

[4] Commercial Solar Sizing & Installation Guidelines, Considerationswhen installing a Solar Thermal

SystemURL:www.kingspansolar.com[5] International Energy Agency, 9, rue de la Fdration75739 Paris

Cedex 15,FranceURL:www.iea.org[6] John A.Duffie, William A.Beckman,2006,Solar Engineering of

Thermal Processes, Third edition, John Willy & Sons, Inc, USA,ISBN-13978-0-471-69867-8.

[7] Large Scale Solar Thermal Systems Design Handbook, A jointPublication between Master Plumbers and Mechanical ServicesAssociation of Australia and Sustainability Victoria,First Edition December 2009.

[8] Literature review of uncertainty of analysis methods, F-ChartProgram, Report to the Texas Commission on Environmental Quality,2004, Texas Engineering Experiment Station Texas A& M UniversitySystem.

[9] Nepal Bureau of Standards, Weather Meteorology, Year 2005, Balajuby pass, Ktm., Nepal Telephone: 350689, 350818

[10] Nepal Oil Corporation, G.P.O.Box : 1140, Babarmahal,Kathmandu,Nepal

[11] Solar Industrial Process Heat ,European Solar thermal IndustryFederation

[12] Solar and Wind Energy Resoource Assessment inNepal,2005,CES,IOE,Pulchowk Campus

[13] Solar Hot water system: The Nepalese Prospect,Center for energystudies ,Institute of Engineering, T.U.International Energy Journal:Special Issue,Vol.3,No.2,December 2002.BY Jagan Nath Shrestha,Raju Rimal, Sheekar Pradhan, Shree Raj Shakya

[14] Solar Thermal Collectors Technical ReferenceURL:www.sunmaxxsolar.com

[15] Sun Works Nepal, Manufacturer of Solar EnergyAppliances,KirtipurSadak,KathamanduURL:www.sunworksnepal.com.np

[16] The Copper tube handbookURL:www.copper.org

[17] Thermomax Design guide URL:www.kingspalsolar.com[18] Unified Facilities Criteria (UFC),Active Solar Preheat Systems,

Department of Defense, USA,December 2007[19] Water and energy commission secretariat ,Singha

Darbar,Kathmandu,Nepal,E-MAIL: [email protected]

diesel fuel consumption reduction in a dairy industry by application of solar thermal technology

Documents